Electric Resistance Welded Pipe

In the ERW HFI manufacturing process, steel coil is mechanically formed into the required pipe diameter, after which a highfrequency electrical current is applied to heat the pipe to fuse the skelp to form a weld. Since no filler material is added, the weld joint becomes a homogeneous part of the completed pipe, thereby ensuring that the required engineering strength and performance specifications are met. See Table 2.

A completely smooth and high quality pipe is ensured via the process of removing the weld beads both internally and externally.

From raw material to finished pipe, the product undergoes the stringent international standard quality testing, thereby guaranteeing you the highest quality:

ERW Pipe Manufacturing Process

The accumulator allows for the steel strip to be continuously fed into the forming section, where the pipes are formed longitudinally using a combination of forming passes and cage technology. This process also incorporates edge forming and is precisely controlled through fine adjustments in the forming cage. Mill set-ups for various diameters, wall thickness and steel grades are recorded in our mill set-up database, thereby ensuring accurate and repetitive quality.

After the forming process, the pipes are welded by high frequency induction (HFI). After welding, the HAZ is seam annealed using medium frequency induction heating and then air cooled. Pipes are then cut to length using a flying cutoff. Pipe lengths between 6 and 18 meters can be produced off the mill. All pipes are then end-faced to prepare pipe-ends for field welding or flanging as required by the customer. All pipes are hydrostatically pressure tested to specification requirements. The weld seams are then again ultrasonically tested by our highly skilled technical staff to ensure no cracks are formed during the pressure test process.

Pipe Coating and Lining process

The external surfaces of pipes have to undergo a comprehensive abrasive cleaning process before any application of coatings can be done. This process consists of external grit blasting, using mechanical impellers.

Grit blasted pipes to SA 2½ are then externally coated. First the pipes are heated by a medium frequency induction process, where after, the pipes enter a spray cabinet where fusion bonded epoxy powder is electro-statically applied to the surface. Pipes then undergo the application of two layers of extruded polymer coatings from two separate consecutive extruders. The first extruder applies a layer of co-polymer adhesive and the second applies a layer of high density polyethylene.

Pipes are then cooled in a quenching bath to ensure that the coating is well cured before handling. The pipe ends are then mechanically brushed to remove the polyethylene coating as required by the specification, to ensure that the coating will not be affected when pipes are joined by butt welding on site.

Capital Star Steel SA, has industry leading technology for the application of protective coatings and linings to steel pipes. The following protective coatings are on offer;